Sorry to contradict everyone here but surely the first piece of advice that one should offer is just general desert info:
I'm presuming from your first post you're new to desert driving and if you were to take this advice and go and have a go in the sand without proper preparation, you could have a rubbish day:
So although tyre deflation is very important, always prepare well to at least a minimum standard (I'm sure others would add more but this is a personal view):
Never go out to the desert alone
Let someone know where you're going and for how long
Take appropriate communications devices, GPS and Water
Take a recovery kit with you and for your tyre pressure, get a decent digital gauge.
Sorry to hijack the thread but thought i'd add my two cents.
Cheers
Nick